Question

Briefly explain why sister chromatids remain together in anaphase i but separate in anaphase ii of meiosis.

Answer 1

Sister chromatids remain together in Anaphase I of meiosis due to the presence of cohesin complexes protected by the protein shugoshin.

What happens during Anaphase of meiosis?

• The anaphase of meiosis differs from that of mitosis.
• In meiosis, a specific cohesin complex is formed which is different from the cohesion proteins of mitosis.
• During the S phase, this complex is formed at the centromere of sister chromatids.
• At the start, cohesion complex is present throughout the chromosome arms and helps in the formation of synaptonemal complex joining the two homologs.
• However during Anaphase I of meiosis, the cohesion molecules are cleaved by separase in the arms region resulting in separation of homologous chromosomes.
• But the cohesin complexes at the centromeres of the sister chromatids is well protected by shugoshin protein which blocks the action of separase.
• Therefore the sister chromatids remain attached during the Anaphase I.
• At the end of metaphase II, the cohesin molecules at the centromeres lose the protection of shugoshin protein.
• Therefore, the separase proteins are able to cleave the cohesin complex, which allows the sister chromatids to separate at Anaphase II.

Learn more about meiosis I here:

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